First study of the safety, tolerability, and pharmacokinetics of CP-724,714 in patients with advanced malignant solid HER2-expressing tumors.

PURPOSE: To test the tolerability, safety, and recommended phase II dose of CP-724,714, a reversible, highly selective, oral HER2 tyrosine kinase inhibitor in patients with advanced solid tumor malignancies that express HER2. EXPERIMENTAL
DESIGN: A phase I trial evaluated escalating doses of CP-724,714, administered daily in 21-day cycles. Pharmacokinetics/pharmacodynamics were evaluated in serial blood samples and in pretreatment and posttreatment tumor and skin biopsies.
RESULTS: Thirty female patients [median age, 51 years (range, 37-71); median performance status, 1 (range, 0-1)] received CP-724,714 at four dose levels: 250 mg once daily (4 patients), 250 mg twice daily (15 patients), 250 mg thrice daily (6 patients), and 400 mg twice daily (5 patients). Dosing at 400 mg twice daily and 250 mg thrice daily was not feasible due to reversible, cholestatic liver dysfunction. Treatment-related adverse events were nausea (58%), asthenia (23%), hyperbilirubinemia (27%), elevated transaminases (30%), and skin rash (30%); neither diarrhea nor cardiomyopathy was observed. No objective responses were observed in 28 evaluable patients; 8 (29%) patients had stable disease. Twenty-seven (96%) patients received prior trastuzumab and were heavily pretreated (median prior chemotherapy, 6; range, 1-11). Systemic exposure exceeded the in vivo efficacy threshold required in preclinical studies.
CONCLUSIONS: Dose-limiting toxicities included hyperbilirubinemia, elevated alanine aminotransferase, thrombocytopenia and pulmonary embolus. Although the protocol-specified maximum tolerated dose of CP-724,714 was 250 mg thrice daily, the recommended phase II dose was 250 mg twice daily due to excessive late-cycle hepatotoxicity. Despite extensive prior treatment, 29% of patients had stable disease. A phase II trial has been initiated in patients with breast cancer.